The reason for the "Modern" suffix to some of these spritesheets is to denote the ones remastered from Sticker Star and Color Splash (the newer Paper Mario games). The non-Modern ones, meanwhile, are either more personalized customs or remasters from the first three Paper Mario games.

Why does it say "modern?" The only parts of the design different from the original design are the lack of feathers, which was an element of their design in both of their Paper Mario appearances, while MLSS+BM, which is newer than both, has the feathers.

There's also the lack of shield, but that's not so much a design element as it is equipment.